CN109016425B

CN109016425B - PE pipe fitting size production control method

Info

Publication number: CN109016425B
Application number: CN201810689113.5A
Authority: CN
Inventors: 张亚军; 张颖; 曾永强; 崔志华; 宋科明
Original assignee: Yunnan Liansu Technology Development Co ltd
Current assignee: Yunnan Liansu Technology Development Co ltd
Priority date: 2018-06-28
Filing date: 2018-06-28
Publication date: 2020-10-20
Anticipated expiration: 2038-06-28
Also published as: CN109016425A

Abstract

The invention relates to a control method, in particular to a control method for the size of a PE pipe fitting product in a production process. (1) Firstly, selecting raw materials and a mould; (2) after the step (1), preparing at least 6 samples of the same specification by using the raw material and the mould of the step (1); (3) after the step (2), carrying out data acquisition, and measuring the outer diameter of the mold core of the mold before injection molding; (4) after the step (3), after the pipe fitting is subjected to core pulling, placing the pipe fitting in an indoor environment with the specified temperature A, and respectively measuring the inner diameter of a pipe fitting socket placed for the specified time; (5) after step (4), the shrinkage was calculated according to the following formula, and the average of the shrinkage of the 6 samples was taken; (6) after the step (5), points are drawn in a coordinate system according to the obtained numerical values, an image is drawn, and the optimal matching function is found by using the principle of least square; the shrinkage rate at a given time can be obtained by a matched function without waiting. The invention can realize the rapid measurement of the size of the PE injection molding pipe fitting without waiting for more than one day.

Description

PE pipe fitting size production control method

Technical Field

The invention relates to a control method, in particular to a control method for the size of a PE pipe fitting product in a production process.

Background

PE pipes have a number of excellent properties: good sanitary performance, no toxicity and no bacteria breeding; excellent corrosion resistance; long service life; the toughness is good, and the impact resistance is good; construction is convenient, and connection is reliable. And thus are widely used in municipal water supply, drainage and gas delivery systems. The PE pipe fitting is an indispensable connecting element of the PE pipeline system, and has a very wide market space.

However, the shrinkage of the PE pipe after injection molding and demolding is large, and the effect of the shrinkage after molding on the pipe size has to be considered, so according to the provisions of GB/T13663.2-2005 clause 7.2: the sample should be taken at least 24 hours after the pipe is produced and measured after conditioning at a temperature of (23 + -2) ° c for at least 4 hours. However, in order to improve the production efficiency and reduce the manufacturing cost in the actual production process, it is necessary to measure and determine whether the product size is qualified as quickly as possible. The current common operating method is as follows: after 24h of production, the pipe dimensions were measured immediately after conditioning for 4h in a (23. + -. 2). degree.C.environment. However, this method has 2 defects:

1. the size can be measured after 28 hours of production, but the actual production process is continuous, the pipe with unqualified size can be found at least after 28 hours, and the produced product needs to be completely scrapped in the period of time. Therefore, the measurement method requires a long waiting time, is not favorable for controlling the product size (especially for matching the size), causes a large amount of unqualified products, and increases the production cost.

"sampling after 24h production, immediately measuring after 4h state adjustment at the temperature of (23 +/-2) ° c" is not scientific because PE injection molded pipes crystallize slowly and have thick walls, and shrink even after being placed in an environment of (23 +/-2) ° c for 10 days, and the current dilemma is that products which are qualified after 24h production are placed in a warehouse for a long time, and the inner diameter of a socket is found to be reduced by re-measuring the size, so that the products are not qualified.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for controlling the size production of a PE pipe fitting.

In order to solve the technical problems, the invention adopts the technical scheme that:

the method for controlling the size production of the PE pipe fitting is characterized by comprising the following specific steps:

(1) firstly, selecting raw materials and a mould;

(2) after the step (1), preparing at least 6 samples of the same specification by using the raw material and the mould of the step (1);

(3) after the step (2), carrying out data acquisition, and measuring the outer diameter of the mold core of the mold before injection molding;

(4) after the step (3) and after the core of the pipe fitting is pulled, placing the pipe fitting in an indoor environment with the specified temperature A, and measuring the inner diameter sizes of the pipe fitting sockets for placing 1h, 2h, 4h, 10h, 24h, 48h, 72h, 96h, 120h, 144h, 168h, 240h, 360h, 480h and 720h respectively;

(5) after step (4), the shrinkage was calculated according to the following formula (1), and the average of the shrinkages of the 6 samples was taken;

shrinkage factor (core outside diameter-bell mouth inside diameter)/core outside diameter × 100% (1);

(6) after the step (5), points are drawn in a coordinate system according to the obtained numerical values, an image is drawn, and the optimal matching function is found by using the principle of least square; the shrinkage rate of the specified time can be obtained through the matched function without waiting;

(7) after step (6), a size control criterion is specified according to the matching function.

The invention provides a method for controlling the size production of a PE pipe fitting, which can realize the rapid measurement of the size of the PE injection molding pipe fitting without waiting for more than one day.

Preferably, in step (4), the temperature a ranges from 21 ° to 25 °.

Preferably, in step (6), the matching function (2) is as follows:

f(x)＝aln(x)+b(x>0) (2)；

wherein the content of the first and second substances,

(x) is the shrinkage of the inner diameter of the pipe socket relative to the mold core;

x is the standing time after core pulling;

a is a coefficient and describes the shrinkage speed of the pipe fitting, the larger the absolute value | a |, the faster the inner diameter of the socket shrinks along with the time, and the slower the inner diameter of the socket shrinks along with the time; taking the first derivative of f (x)

Is an inverse proportional function, namely, the contraction rate is slowed down along with the extension of the placing time, and when the placing time is long enough, the contraction rate approaches 0, the contraction is stopped;

b is the translation coefficient.

Preferably, the values of the coefficients a, b are determined by taking the average of the shrinkage of 6 samples.

Preferably, according to the formula of the matching function (2), the rapid measurement of the dimensions of the PE injection molded pipe is realized without waiting for more than one day.

Preferably, in step (1), the starting material: the prepared sample uses the raw materials of the same manufacturer, the same brand and the same batch and the same auxiliary materials; a mould: the moulds used for preparing the samples are moulds with the same batch, the same design structure, the same material and the same cooling system.

Preferably, the coefficient a is determined by raw material variation, mold structure, and molding process.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a method for controlling the size production of a PE pipe fitting, which can realize the rapid measurement of the size of the PE injection molding pipe fitting without waiting for more than one day. .

Drawings

FIG. 1 is a recorded graph of shrinkage margins of a non-specific sample model of a PE pipe dimension production control method of the present invention.

FIG. 2 is a graph of shrinkage for the given sample parameters of example one.

FIG. 3 is a chart of shrinkage margin records for specified sample parameters of example one.

FIG. 4 is a graph of shrinkage for the specified sample parameters of example two.

FIG. 5 is a plot of shrinkage margin records for specified sample parameters for example two.

FIG. 6 is a graph of shrinkage for the specified sample parameters of example three.

FIG. 7 is a plot of shrinkage margin records for specified sample parameters for example three.

FIG. 8 is a graph of shrinkage for the specified sample parameters of example four.

FIG. 9 is a plot of shrinkage margin records for specified sample parameters for example four.

FIG. 10 is a graph of shrinkage for the specified sample parameters of example five.

FIG. 11 is a plot of shrinkage margin records for specified sample parameters for example five.

FIG. 12 is a graph of shrinkage for the specified sample parameters of example six.

FIG. 13 is a plot of shrinkage margin records for specified sample parameters for example six.

Detailed Description

The present invention will be further described with reference to the following embodiments. Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not intended to indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms may be understood by those skilled in the art according to specific circumstances.

Example 1

Referring to fig. 1 to 3, an embodiment of a method for controlling the dimension of PE pipe according to the present invention is shown, which comprises the following specific steps

The method comprises the following steps:

(1) firstly, selecting raw materials and a mould;

Wherein, in the step (4), the temperature A is in the range of 21-25 deg.

In addition, in step (6), the matching function (2) is as follows:

f(x)＝aln(x)+b(x>0) (2)；

wherein the content of the first and second substances,

x is the standing time after core pulling;

b is the translation coefficient.

Wherein, the average value of the shrinkage rates of 6 samples is taken to determine the values of the coefficients a and b.

In addition, according to the formula of the matching function (2), the size of the PE injection molding pipe fitting can be measured quickly without waiting for more than one day.

Wherein, in step (1), the raw material: the prepared sample uses the raw materials of the same manufacturer, the same brand and the same batch and the same auxiliary materials; a mould: the moulds used for preparing the samples are moulds with the same batch, the same design structure, the same material and the same cooling system.

The coefficient a is determined by the change of raw materials, the structure of the mold, and the molding process.

Specifically, the method comprises the following steps: assuming that the outer diameter of the mold core is D, the inner diameter of the socket measured at a certain time point after core pulling is D_iAnd the shrinkage of the pipe after 30 days is negligible (according to the specific implementation case, the shrinkage from 25 days to 30 days can be calculated to be small, the tolerance of the relative product requirement can be ignored, the shrinkage of the pipe after 30 days can be considered to stop, see the implementation case in detail), then the inner diameter of the socket after the pipe is stabilized is d_i-Δd_iShrinkage margin Δ d at different measurement times_iAs shown in fig. 1 below (when a is given, a specific numerical value can be calculated).

According to the graph 1, the size of the final pipe fitting after stabilization can be predicted by measurement within a short time after core pulling, whether the product is qualified or not can be judged according to the size standard requirement, and the time of waiting for more than 1 day is not needed.

However, it should be noted that the coefficient a is determined based on the conditions that the raw material is not changed much, the mold structure is the same, and the molding process is the same, so that once it is determined that some factor that may affect the coefficient a occurs, the coefficient a should be determined again. Generally, the same set of mold, the same grade of material (including auxiliary material), the same molding process, the same coefficient a.

Specific values given are: when the sample parameters are: when the outside diameter of the die core is 111.80mm, the image of shrinkage rate obtained according to the formula of the matching function (2) and the specific measurement steps is shown in fig. 2. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a can be determined to be 0.0005. In addition, the shrinkage of the product is not more than 0.01mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 3.

Example two:

as shown in fig. 4 to 5, this embodiment is similar to the embodiment except that the parameters of the sample are changed. The sample parameters were: dn110PE electric smelting straight through, the outer diameter of the mold core is 112.00mm, and the shrinkage rate image obtained according to the formula of the matching function (2) and the specific measurement steps is shown in fig. 4. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a is determined to be 0.00065.

In addition, the shrinkage of the product is not more than 0.01mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 5.

Example three:

as shown in fig. 6 to 7, this embodiment is similar to the embodiment except that the parameters of the sample are changed. The sample parameters were: dn160PE electrofusion straight-through, mold core outer diameter 162.60mm, shrinkage ratio image according to the formula of the matching function (2) and the specific measurement steps is shown in fig. 6. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a is determined to be 0.00065.

In addition, the shrinkage of the product is not more than 0.02mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 7.

Example four:

as shown in fig. 8 to 9, this embodiment is similar to the embodiment except that the parameters of the sample are changed. Sample preparation: the dn160 × 90 ° PE electrofused elbow, the outer diameter of the mold core was 162.80mm, and the shrinkage ratio image obtained according to the formula of the matching function (2) and the specific measurement steps is shown in fig. 8. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a is determined to be 0.00064.

In addition, the shrinkage of the product is not more than 0.02mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 9.

Example five:

as shown in fig. 10 to 11, this embodiment is similar to the embodiment except that the parameters of the sample are changed. Sample preparation: dn90PE electrofusion tee joint, mold core outer diameter 91.55mm, shrinkage ratio image obtained according to the formula of the matching function (2) and the specific measurement steps is shown in fig. 10. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a is determined to be 0.00067.

In addition, the shrinkage of the product is not more than 0.01mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 11.

Example six:

as shown in fig. 12 to 13, this embodiment is similar to the embodiment except that the parameters of the sample are changed. Sample preparation: and dn200PE are directly fused, the outer diameter of the mold core is 203.20mm, and the steps are carried out. The image of shrinkage resulting from the formulation of the matching function (2) and the specific measurement procedure is shown in fig. 12. The curve with points is the measured value, the curve without points is the best matching function, and the coefficient a can be determined to be 0.0005. In addition, the shrinkage of the product is not more than 0.02mm from 25 days to 30 days, the relative requirement tolerance is negligible, and the pipe fitting is considered to be stable after 30 days. The shrinkage margin Δ di at different measurement times is shown in FIG. 13.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A PE pipe fitting size production control method is characterized by comprising the following specific steps:

(1) firstly, selecting raw materials and a mould;

(7) after step (6), specifying a size control criterion according to the matching function;

wherein, in the step (4), the temperature A is in the range of 21-25 degrees;

in step (6), the matching function (2) is as follows:

f(x)＝a ln(x)+b(x>0) (2)；

wherein the content of the first and second substances,

(x) is the shrinkage of the inner diameter of the pipe socket relative to the outer diameter of the core;

x is the standing time after core pulling;

b is the translation coefficient.

2. A method for controlling the dimensional production of PE pipe according to claim 1, characterized in that the values of the coefficients a, b are determined by taking the average of the shrinkage of 6 samples.

3. The PE pipe dimensioning control method according to claim 2, characterized in that, according to the formula of the matching function (2), a fast measurement of the dimensions of the PE pipe is achieved without waiting for more than one day.

4. The PE pipe sizing control method according to claim 2, wherein in step (1), the raw material: the prepared sample uses the raw materials of the same manufacturer, the same brand and the same batch and the same auxiliary materials; a mould: the moulds used for preparing the samples are moulds with the same batch, the same design structure, the same material and the same cooling system.

5. The method of claim 2, wherein the factor a is determined by the raw material, the die structure, and the forming process.